A family of Mn-III/Ni-II heterometallic clusters, [(Mn4Ni5II)-Ni-III(OH)(4)(hmcH)(4)(pao)(8)Cl-2]center dot 5DMF (1 center dot 5DMF), [(Mn3Ni6II)-Ni-III(N-3)(2)(pao)(10)(hmcH)(2)(OH)(4)]Br center dot 2MeOH center dot 9H(2)O (2 center dot 2MeOH center dot 9H(2)O), [(MnNi5II)-Ni-III(N-3)(4)(pao)(6)(paoH)(2)(OH)(2)](CiO(4))center dot MeOH center dot 3H(2)O (3 center dot MeOH center dot 3H(2)O), and [(Mn2Ni2II)-Ni-III(hmcH)(2)(pao)(4)(OMe)(2)(MeOH)(2)]center dot 2H(2)O center dot 6MeOH (4 center dot 2H(2)O center dot 6MeOH) [paoH = Pyridine-2-aldoxime, hmcH(3) = 2, 6-Bis(hydroxymethyl)-p-cresol], has been prepared by reactions of Mn(II) salts with [Ni(paoH)(2)Cl-2], hmcH(3), and NEt3 in the presence or absence of NaN3 and characterized. Complex 1 has a (Mn4Ni5II)-Ni-III topology which can be described as two corner-sharing [Mn2Ni2O2] butterfly units bridged to an outer Mn atom and a Ni atom through alkoxide groups. Complex 2 has a (Mn3Ni6II)-Ni-III topology that is similar to that of 1 but with. two corner-sharing [Mn2Ni2O2] units of 1 replaced with [Mn3NiO2] and [MnNi3O2] units as well as the outer Mn atom of 1 substituted by a Ni atom. 1 and 2 represent the largest 3d heterometal/oxime clusters and the biggest (MnNiII)-Ni-III clusters discovered to date. Complex 3 possesses a [MnNi5(mu-N-3)(2)(mu-OH)(2)](9+) core, whose topology is observed for the first time in a discrete molecule. Careful examination of the structures of 1-3 indicates that the Mn/Ni ratios of the complexes are likely associated with the presence of the different coligands hmcH(2-) and/or N-3(-). Complex 4 has a Mn(III)2Ni(2)(II) defective double-cubane topology. Variable-temperature, solid-state dc and ac magnetization studies were carried out on complexes 1-4. Fitting of the obtained M/(N mu(B)) vs H/T data gave S = 5, g = 1.94, and D = -0.38 cm(-1) for 1 and S = 3, g = 2.05, and D = -0.86 cm(-1) for 3. The ground state for 2 was determined from ac data, which indicated an S = 5 ground state. For 4, the pairwise exchange interactions were determined by fitting the susceptibility data vs T based on a 3-J model. Complex 1 exhibits out-of-phase ac susceptibility signals, indicating it may be a SMM.